1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition that when exposed to actinic rays or radiation, makes a reaction to thereby change its properties and a method of forming a pattern using the composition. More particularly, the present invention relates to an actinic-ray- or radiation-sensitive resin composition for use in a semiconductor production process for an IC or the like, the production of a liquid crystal, a thermal head or the like, the fabrication of a nanoimprint mold structure, other photofabrication processes, a lithographic printing plate and a thermosetting composition and also relates to a method of forming a pattern with the use of the composition.
In the present invention, the terms “actinic rays” and “radiation” mean, for example, brightline spectra from a mercury lamp, far ultraviolet represented by an excimer laser, extreme ultraviolet, X-rays, electron beams and the like. In the present invention, the term “light” means actinic rays or radiation.
2. Description of the Related Art
A resist composition of chemical amplification type is a pattern forming material that is capable of, upon exposure to far ultraviolet or other radiation, generating an acid in exposed areas and, by a reaction catalyzed by the acid, changing the solubility in a developer between the areas having been exposed to actinic radiation and the nonexposed areas to thereby attain pattern formation on a substrate.
When a KrF excimer laser is used as an exposure light source, a resin whose fundamental skeleton is composed of a poly(hydroxystyrene) exhibiting a low absorption mainly in the region of 248 nm is employed as a major component of a resist composition. Accordingly, there can be attained a high sensitivity, high resolution and favorable pattern formation. Thus, a system superior to the conventional naphthoquinone diazide/novolak resin system is realized.
However, in using a light source of a further shorter wavelength, for example, an exposure light source of an ArF excimer laser (193 nm), as the compounds containing aromatic groups inherently exhibit a sharp absorption in the region of 193 nm, the above-mentioned chemical amplification system has not been satisfactory.
Consequently, resists for ArF excimer laser containing a resin with an alicyclic hydrocarbon structure have been developed.
It is of conventional practice to use compounds capable of generating a perfluoroalkanesulfonic acid, such as trifluoromethanesulfonic acid or nonafluorobutanesulfonic acid, as a photoacid generator. To now, it has been proposed to use photosensitive compositions comprising compounds capable of generating specified sulfonic acids (see, for example, patent references 1 to 4) and to use photosensitive compositions comprising a compound capable of generating any of specified sulfonic acids and a resin that when acted on by an acid, is decomposed to thereby increase its solubility in an alkali developer (see, for example, patent references 5 and 6).
When use is made of, for example, a light source emitting electron beams, X-rays or EUV, the exposure is carried out in vacuum. This tends to cause any low-boiling-point compounds, such as solvents, and resist materials decomposed by high energy to evaporate to thereby dirty the exposure apparatus. This outgas problem is becoming serious. In recent years, various researches have been made on the reduction of the outgas. Various proposals have been made, which include a proposal to inhibit the evaporation of low-molecular compounds by providing a top coat layer (see, for example, patent reference 7) and a proposal to add a radical trapping agent for the inhibition of any polymer decomposition (see, for example, patent reference 8). For the acid generator as well, an ingenuity for outgas reduction is demanded.
Now, there is a demand in the art for the development of a photosensitive composition that is enhanced in not only the outgas reduction but also the sensitivity, resolution, pattern configuration, roughness characteristic, aging stability, etc. through improvement of such acid generators.
In particular, the roughness characteristic and resolution become serious in accordance with the reduction of the pattern dimension. In the lithography using X-rays, electron beams or EUV, as the formation of a fine pattern of several tens of nanometers is targeted, the demand for excelling in the resolution and roughness characteristic is especially strong.